A 48-year-old woman has a 3-week history of fatigue as well as yellow skin and sclerae. Physical examination is unremarkable except for mild jaundice. The serum bilirubin level is 3.7 mg/dL, mostly in the unconjugated form. Liver function tests including serum AST, ALT, and alkaline phosphatase are normal. The hemoglobin level is 6.0 g/dL. After corticosteroids are administered, the jaundice resolves. Which of the following diseases is the most likely cause of hyperbilirubinemia in this patient?

Autoimmune hemolytic anemia is characterized by antibody-mediated erythrocyte destruction and may lead to severe anemia, as in this case. Intravascular hemolysis produces increased serum levels of unconjugated bilirubin, which exceed the capacity of the hepatocyte to conjugate bilirubin. In most cases, the disease is ameliorated by treatment with corticosteroids. The other choices are parenchymal liver diseases that manifest primarily as conjugated hyperbilirubinemia and are unresponsive to steroids.Diagnosis: Autoimmune hemolytic anemia